ES2205912T3 - CONTINUOUS COATING PROCEDURE AND DEVICE FOR AT LEAST ONE METAL TAPE THROUGH A FLUID FILM OF RETICULABLE POLYMER. - Google Patents

Abstract

Continuous coating process of at least one metal band (1) by a fluid film (31) of crosslinkable polymer free of solvent or non-reactive diluent and whose softening temperature is greater than 50 ° C, said film (31) having a thickness less than that of the metal band, according to which: - the metal band (1) is continuously displaced on at least one cylinder of the support (3), - is formed, on a deformable surface applicator cylinder (20) and by forced flow at a temperature greater than the softening temperature of the crosslinkable polymer, a layer (30) of said crosslinkable polymer in the molten state, having a viscosity greater than 10 Pa.s under the conditions of formation of said layer, being the forming temperature of this layer (30) is lower than the temperature at the beginning of the crosslinking of the crosslinkable polymer and said applicator cylinder (20) being rotated in a reverse direction to The direction of travel of the metal band (1), - the crosslinkable polymer film (31) is formed on the applicator cylinder (20), - a total thickness transfer of the film (31) of the cylinder is carried out applicator on the metal band (1), compressing this metal band between the support cylinder (3) and the applicator cylinder (20) to obtain a coating of homogeneous thickness.

Description

Procedure and coating device in continuous of at least one metal tape using a film crosslinkable polymer fluid.

The present invention aims at a procedure and a continuous coating device of by at least one metal band for a fluid and small film thickness of solvent-free or diluent crosslinkable polymer not reactive.

Polymers that are crosslinkable via route are known. thermal, such as thermosetting polymers, or via physics, such as photopolymerizable polymers.

There is a wide variety of coatings thermosetting organics that are applied continuously on metal substrates

In most cases, it is about complex formulas that associate in a solvent or aqueous medium a prepolymer functional organic binder system, a crosslinking system and additives such as pigments or fillers, various formulation aids.

Various methods of application of a thermoplastic organic coating or thermosetting on a bare or coated metal band.

The application of organic coatings such as liquid paints or varnishes, the most currently by roller coating of these coatings liquids in a state of solution or dispersion in solvent medium or aqueous.

To do this, the deposit of the liquid coating on a metal band, making a after dosing the solution or dispersion thanks to a two or three roller system and transferring a part or the all of this liquid coating thus previously dosed at an applicator roller brought into contact with the surface of the metal band that is to be coated.

The transfer is done either by friction of the applicator roller and the metal band, the displacement of the two surfaces in contact in direction On the contrary, either by contact in the same direction.

An interesting evolution of the technology of continuous application of polymer coatings crosslinkable, such as thermosetting paints or varnishes on a metal band is to make the deposit of this coating without involving solvent or diluent.

Several alternatives have been proposed for processing and application of organic coatings without employment of solvent or non-reactive diluent.

But the realization poses a double problem, the of the realization of a homogeneous dispersion of the charges and of the pigments in the binder system and the application of the product thus obtained.

One of the techniques used for the application of such coatings consists in applying the organic coating in the form of a powder.

Another application technique is also known. of a liquid coating on a metal band that uses a Heater tank commonly called smelter, endowed in its bottom of a passage hole of the liquid polymer contained In the deposit.

Below this deposit are arranged two parallel cylinders and in contact with each other and the band metal that is to be coated is shifted below these cylinders

The liquid polymer is poured at the level of air gap of the cylinders, and then is flowed between said cylinders and is deposited on the metal band.

But this technique has drawbacks, which they reside in the fact that the polymer can only be little reactive, taking into account its relatively long time spent in the heater tank and the fact that it does not allow to regulate the thickness of the coating film on the metal strip and therefore obtain a homogeneous and low coating thickness.

To make thin deposits of products viscous organic, another technique is to use extrusion of the organic coating in fluid state and in applying this coating on a substrate by layer deposit or by lamination.

The extrusion and layer deposition of a thin organic coating is commonly practiced in particularly with thermoplastic polymers on flexible surfaces, like paper, plastic films, textiles, even Thin metal supports such as packing materials.

The application of the molten coating is performed by means of a rigid flat row or a nozzle or nozzle located in direct contact with the substrate.

The pressure exerted by the row on the substrate comes from the viscosity of the molten matter. So, the possibilities of correcting the flatness defects of the substrate by applying it on the support cylinder are very limited

This extrusion technique and layer application demands a perfect parallel between the edges of the row and the substrate and this substrate must be either perfectly flat, or well deformable, to allow the formation of a thin deposit of uniform thickness.

Indeed, the thickness of deposited matter is regulates by the play and the pressure between the row and the substrate, what which imposes a perfect parallelism of these two elements when You want to make applications in a very small thickness.

This condition is not realizable in the case of steel bands between 0.3 and 2 mm thick, which they have a rigidity too important and a flatness or a insufficient thickness regularity to allow such a fit exact game between the row and the substrate, particularly in the case of large bands.

The technique of extrusion-lamination of a uniform layer of fluid coating on a substrate uses low stretch the row of a fluid layer at the exit of a flat row, then applying this layer on the substrate using for example a cold roller, a rotating bar or a sheet of air or an electrostatic field.

In this case, the thickness of the fluid layer is regulates by the flow of the matter in the section of the row and by the speed of the substrate.

In case of gluing of the fluid layer on the application roller, the layer would be separated into two parts in its thickness, a part being applied to the substrate and remaining applied the other part on the roller. This layer separation it implies that the transfer is not total and that the coating obtained on the substrate does not present a surface appearance satisfactory nor a uniform thickness.

To avoid adhesion of the fluid layer on the application roller, it must have a surface perfectly smooth and cooled.

The application pressure must, however, be loose enough to prevent the formation of an impeller calendering and, thus, this form of transfer does not allow compensation eventual variations in thickness and flatness defects in the case of a rigid substrate.

This coating application technique with formation of a free segment at the exit of the extrusion row allows to avoid the problems of coupling between the row and the rigid substrate, but induces application instabilities if the Free segment length fluctuates and is difficult to perform with thermosetting systems with a viscosity of less than 2000 Pa.s due to the difficulties in performing a regular stretching and a good application.

In general, in the different known techniques that are listed here, the continuous application of a thin organic coating on metal substrates is effected under low contact pressures, insufficient to allow make a thin, uniform and applied coating homogeneous on rigid substrates that may present defects of flatness and heterogeneity of thickness.

These different application techniques do not allow compensation of substrate thickness variations metallic, thus inducing unacceptable fluctuations in thickness of the coating particularly in case the substrate is formed by a metal band that has a roughness and / or some significant surface undulations of equal or greater amplitude to the thickness of the coating that is to be performed on said metal band

Moreover, these different techniques of application does not allow to accommodate variations in width of the substrate, or to transverse placement variations of this substrate, so that the coating cannot be deposited so uniform across the entire width of the substrate.

Finally we will say that, in the course of the coating application, can be interleaved micro-bubbles of air between the lining and the substrates, which harm the homogeneous application and the appearance of surface of this coating.

Thus, the continuous application of a Crosslinkable polymer coating of small thickness and uniform on a metal band poses problems, due to the fact that this metal band presents flatness and thickness defects, as well as a roughness and / or significant undulations of amplitude equal to or greater than the thickness of the coating film that is try to deposit on that band, even if this band has applied under high tension on a uniform cylinder.

In addition, the different techniques used up to the present does not allow to apply on a metal band a small thickness coating, crosslinkable polymer, free of solvent or non-reactive diluent that meets two requirements contradictory, which are hardness and deformability.

Indeed, after crosslinking, the polymer coating must be hard enough at the time that deformable to allow the configuration of the plates as well coated without causing degradation or separation of coating.

Now it is known that the elevation of the mass Molecular of the polymer crosslinkable precursors is very favorable for obtaining a final coating at a time hard and deformable.

But the elevation of the molecular mass of precursors has a very unfavorable effect on the viscosity of a solvent-free or non-reactive diluent polymer, which does not favor the transfer or application of the layer on the metal band

It is also known in the current state of the technique, US-A-5 407 702 which describes a procedure and a coating device in continuous of a metal band by a fluid polyester film high viscosity by continuous displacement of the band metal on a support cylinder forming a layer of said polyester by forced flow on a surface cylinder hard, and after the aforementioned film from said layer, and of transfer of said film on the metal strip, by intermediate several intermediate transfer cylinders.

It is also known within the current state of the technique, according to Article 54 (3) CBE, the document EP-A-1 001 848, which describes a procedure and a continuous coating device of by at least one metal band per a fluid polymer film crosslinkable solvent-free or thinner-free and thinner to the metal band. The device comprises:

- continuous means of dragging the band metallic,

- at least one band support cylinder metallic,

- band preheating means metal at a temperature equal to or greater than the temperature of the fluid film of crosslinkable polymer and at the temperature of softening of this crosslinkable polymer,

- training means on a cylinder hard surface receiver, by forced flow of a homogeneous layer and of uniform thickness of said crosslinkable polymer,

- and a surface applicator element deformable, compressed between the receiving cylinder and the band metallic

The receiving cylinder according to the document EP-A-1 001 848 is surface hard.

The object of the invention is to propose a procedure and a continuous coating device of by at least one metal band for a fluid and small film thickness of solvent-free or diluent crosslinkable polymer non-reactive and whose softening temperature is higher than 50 ° C, allowing to obtain a coating of a uniform thickness of a few microns to a few tens of microns applied so homogeneous on this band, while avoiding micro-bubbles of air that are interspersed between the film and metal band and no worry about the defects of flatness and roughness of this band, as well as allowing a application on part or all of the coating, and this despite the fluctuations in width and transverse position of this band

The object of the invention is therefore a continuous coating process of at least one band metallic by a fluid film of crosslinkable polymer free of solvent or non-reactive diluent and whose temperature of softening is greater than 50 ° C, said film having a thickness less than the metal band, according to which:

- the metal band is moved continuously on at least one support cylinder,

- is formed on an applicator cylinder of deformable surface and forced flow at a higher temperature at the softening temperature of the crosslinkable polymer, a layer of said melt crosslinkable polymer having a viscosity greater than 10 Pa.s under the conditions of formation of said layer, the forming temperature of this lower layer being at the temperature of the polymer crosslinking principle crosslinkable and the said applicator cylinder being dragged in rotation in the opposite direction to the direction of band movement metallic,

- the applicator cylinder is formed on crosslinkable polymer film,

- a total thickness transfer is made of the film, of the applicator cylinder on the metal strip, compressing this metal band between the support cylinder and the applicator cylinder, to obtain a thick coating homogeneous.

The object of the invention is also a continuous coating device of at least one band metallic by a fluid film of crosslinkable polymer free of solvent or non-reactive diluent and whose temperature of softening is greater than 50 ° C, said film having a thickness less than that of the metal band, said said device:

- continuous means of dragging the band metallic,

- at least one band support cylinder metallic,

- training means on a cylinder deformable and forced flow surface applicator to a temperature exceeding the softening temperature of crosslinkable polymer, of a layer of said crosslinkable polymer in molten state, of a viscosity greater than 10 Pa.s in the formation conditions of said layer, the temperature being formation of this layer below the temperature of the beginning of crosslinking of the crosslinkable polymer and being entrained in rotation said applicator cylinder in the opposite direction to the direction of displacement of the metal band and forming the film of crosslinkable polymer,

- and compression compression means of the metal band between the support cylinder and the applicator cylinder to effect a total transfer in thickness of said film of the applicator cylinder on the metal band and get a homogeneous thickness coating.

The characteristics and advantages of the invention they will appear in the course of the description that follows, given only by way of example and made with reference to the attached drawings, in which:

- fig. 1 is a schematic sectional view of an installation of coating a metal band by a crosslinkable polymer film comprising a device of application of this coating according to the invention,

- fig. 2 is a schematic view in perspective of the application device according to the invention and provided with a first embodiment of suppression means of excess crosslinkable polymer,

- fig. 3 is a schematic view on perspective of the application device according to the invention and provided with a second embodiment of suppression means of excess crosslinkable polymer.

In fig. 1, has been schematically represented a continuous coating installation of a metal strip 1 by a fluid crosslinkable polymer film, free of solvent or non-reactive diluent of thickness comprised of example between 5 and 50 µm.

This metal band has a thickness included for example between 0.10 and 4 mm and is for example steel or aluminum or also of an aluminum alloy, and may be coated or previously painted on one or both sides.

The polymer used to cover the band metallic 1 is a solvent-free or non-diluent polymer reactive and thermally crosslinkable such as a polymer thermosetting or by physical means such as a polymer light curing This polymer has an uncrosslinked state softening temperature greater than 50 ° C.

These polymers have temperatures of softening of flow principle, of cross-linking principle and fast crosslinking that are different.

In general, the beginning temperature of crosslinking is the temperature from which a viscosity increase greater than 10% in less than 15 minutes.

In the embodiment shown in the fig. 1, the metal band 1 is driven in displacement according to the arrow F and this metal band 1 rests on at least one support cylinder 3 comprising a metal central bore 3a, such as steel, and an outer shell 3b of material deformable, such as elastomer.

The support cylinder 3 can also be constituted by a steel cylinder.

The installation comprises means 2 of preheating the metal band 1 at a temperature substantially equal to or greater than the temperature of the film crosslinkable polymer fluid that is deposited on said metal band 1 and at the softening temperature of this crosslinkable polymer.

The band preheating means 2 metallic 1 are constituted for example by at least one oven induction

As depicted in fig. 1, the Installation includes, from front to rear:

- a device designated as a whole by the reference 10 of coating the metal band 1 by a fluid, solvent free or crosslinkable polymer film non-reactive diluent and whose softening temperature is above 50 ° C,

- means 5 for cooking or crosslinking of the crosslinkable polymer film,

- and a traction block 7 of the metal band 1.

In the event that the polymer is crosslinkable by thermally, the cooking means 5 will comprise, for example, the minus an induction oven and cooling means 6 and in the if the polymer is physically crosslinkable, the means 5 cooking may consist of lightning lamps ultraviolet or by electron beams.

Referring below to figs. 2 and 3, we will describe the band coating device 10 metal 1 by a fluid crosslinkable polymer film.

This crosslinkable polymer film for deposit on metal band 1 must be of uniform thickness, although this metal band 1 has thickness heterogeneities or flatness defects as well as roughness and / or undulations of important surface of amplitude equal to or greater than the thickness of the film deposited on said metal band 1.

The coating device 10 comprises:

- training means 11 and 12, on a deformable surface applicator cylinder 20, by forced flow of a homogeneous and uniform layer of polymer thickness 30 crosslinkable, with a viscosity greater than 10 Pa.s and preferably between 20 Pa.s and 2000 Pa.s under the conditions of formation of said layer 30, said applicator cylinder 20 forming a crosslinkable polymer film 31 of uniform thickness and substantially equal to the desired thickness,

- and a band compression means metal 1 between the support cylinder 3 and the applicator cylinder 20 to effect a total transfer in thickness of said film 31 of the applicator cylinder 20 on the metal strip 1 and obtain a homogeneous thickness coating.

A transfer is considered as total or almost total thickness when more than 90% of the transfer has been transferred matter.

Layer 30 is formed by forced flow to a temperature exceeding the softening temperature of crosslinkable polymer.

In addition, the formation temperature of layer 30 is lower than the temperature of the beginning of crosslinking of the polymer.

The means of forced flow training of the crosslinkable polymer layer 30 comprise for example a machine Extrusion not shown, classic type, equipped with a row 11 having an extrusion groove 12 and a regulating body by the way, not represented, constituted for example by a pump dosing machine and arranged between the extrusion machine and the row eleven.

The applicator cylinder 20 comprises a bore metallic central 21, such as steel, and a wrapper external 22 of deformable material, such as elastomer.

The applicator cylinder 20 is heated to a temperature substantially equal or higher, on the one hand, to the forming temperature of layer 30 and, on the other hand, at softening temperature of the crosslinkable polymer, and is dragged in rotation by appropriate means not shown, in a reverse direction to the direction of band movement metallic, as represented by arrows f1 in figs. two and 3.

With respect to the support cylinder 3 of said metal band 1, the applicator cylinder 20 is driven in rotation in the same direction as this cylinder 3.

The formation of layer 30 of said polymer crosslinkable is done for example by extrusion-application in layer or by extrusion and lamination.

In the case of layer extrusion-application, as has been represented in figs. 2 and 3, the means of flow training forced layer 30 are formed by row 11 resting against the surface of the applicator cylinder 20 and provided with means of regulation, of the classical type, of the position of the edges of the extrusion groove 12 of said row 11 with respect to the said surface of the applicator cylinder 20.

Row 11 of the extrusion machine gives the uniform distribution of layer 30 that is obtained by operating on the step or flow of row 11 and the rotation speed of applicator cylinder 20.

Row 11 is resting on the cylinder applicator 20 for example by means of cats not represented whose pressure allows the polymer leakage rate to be uniform crosslinkable fluid.

Due to the perfect parallelism of row 11 and of the applicator cylinder 20, a layer 30 of uniform thickness

In the case of extrusion-lamination, the means of formation by forced flow of layer 30 are formed by row 11, about means for stretching layer 30 by adjusting the flow rate or passage of this row 11 and / or the speed of rotation of the cylinder applicator 20, a means of regulating the classic type of position of the edges of the extrusion groove 12 of said row 11 in relation to the surface of the receiving cylinder 20 and about means, not shown, of application of layer 30 on said surface of the applicator cylinder 20.

The means of application of layer 30 on the surface of the applicator cylinder 20 are formed for example by a sheet of air directed towards the applicator cylinder 20 at the level of the contact generator of said layer 30 on the mentioned applicator cylinder 20.

The internal heating system is constituted for example by inserted electrical resistors in the bore of the applicator cylinder 20 or through arranged channels in said bore for the circulation of a fluid such as oil.

The internal temperature of the applicator cylinder 20 must be regulated, such as by a thermoelectric pair not represented, so as not to exceed a limit value to avoid damaging the outer shell 22 made of deformable material by a temperature too high and deteriorate the bonding layer between the deformable material and the metal bore of said applicator cylinder twenty.

The coating device 10 comprises also means, not shown, of pressure regulation of contact between the applicator cylinder 20 and the metal strip 1.

These means are constituted for example by hydraulic jacks or systems of screw-nut and allow to adjust this pressure of contact depending on the viscosity of the crosslinkable polymer for ensure a total transfer of matter and minimize friction efforts.

As depicted in figs. 2 and 3, the extrusion groove 12 of row 11, as well as the cylinder applicator 20 have a length greater than the width of the band metal 1, to cover the entire surface of the face of this metal band 1 in contact with the applicator cylinder 20.

According to a variant, the extrusion groove 12 of row 11 and applicator cylinder 20 may have a length less than the width of the metal band 1 to cover no more than a part of the surface of the face of said metal band 1 in contact with the applicator cylinder 20.

The application of fluid film 31 and small thickness in polymer crosslinkable thermally or via Physics is done as follows.

The metal band 1 is maintained at a temperature equal to or greater than the softening temperature of the polymer crosslinkable and the applicator cylinder 20 is dragged in rotation in the reverse direction to the direction of travel of this band metallic 1.

As an example, we will say that the band metallic 1 is preheated to a temperature of 140 ° C immediately before its passage to the support cylinder 3 and it moves at a speed of 30 m / mn.

At the exit of row 11 of the machine extrusion, layer 30 formed by forced flow at a temperature higher than the softening temperature of the polymer is applied on the applicator cylinder 20 to form the film 31 of crosslinkable polymer of corresponding uniform thickness substantially to the thickness of the coating in formation on the metal band 1.

As an example, we will say that the slot of extrusion 12 of row 11 has an opening of a height of 300 µm regulated by a metal insert over a width of 350 mm application. This row 11 rests on the cylinder applicator 20 by means of for example cats whose pressure is adjustable and allows the polymer leakage rate to be uniform crosslinkable

Due to the pressure exerted on the band metal 1 by the applicator cylinder 20 and the support cylinder 3 deformable surface, the entire film is transferred 31 of the applicator cylinder 20 to the surface of the metal strip 1 That is about covering.

Then the metal band 1 thus coated goes to cooking means 5, and then to means 6 of cooling of the crosslinkable polymer film 31.

This crosslinkable polymer film 31 can be placed on a bare metal band of steel or aluminum or of an aluminum alloy or on a metal band previously coated or previously painted on one of its two faces or on both.

The coating thus made on the band metallic 1 has for example a thickness between 5 and 100 um with a thickness uniformity of a few microns and this at despite the notable flaws of flatness or heterogeneity of thickness of the metal band 1.

Other means of training can be used by forced flow of layer 30.

Thus, the means of flow training forced layer 30 can be formed by a projection system of fluid crosslinkable polymer on the applicator cylinder 20 or by an application system on this applicator cylinder 20 of a continuous band of crosslinkable polymer previously made for form layer 30.

Layer 30 and polymer film 31 crosslinkable may have a width less than the width of the metal band 1 to cover a part of this metal band 1 or a width greater than the width of this metal band 1 for cover the entire surface of said metal band 1.

In the case that layer 30 and film 31 have a width greater than the metal band 1, as has been represented in figs. 2 and 3, subsists on either side of the useful area of application on said metal band 1, a portion of crosslinkable polymer that is not applied on this metal band 1.

This excess of crosslinkable polymer is due remove in order to avoid creating an excess thickness on the applicator cylinder 20.

For this, the coating device is equipped with means 40 to suppress excess polymer crosslinkable deposited on the applicator cylinder 20.

According to a first embodiment depicted in fig. 2, means 40 to suppress excess of crosslinkable polymer deposited on the applicator cylinder 20 are formed by two rails, 41a and 41b, respectively, for example metallic, in contact with the applicator cylinder 20 in each zone located outside the contact area of said cylinder applicator 20 with metal strip 1.

The rails 41a and 41b are in contact with the applicator cylinder 20 ahead of the application generatrix of the layer 30 on this applicator cylinder 20 in relation to the direction of rotation of said applicator cylinder 20.

The transverse position of the rails 41a and 41b on the applicator cylinder 20 may be held, by means appropriate not shown, to the width of the metal band and / or to the transverse position of this metal band 1 on the cylinder of support 3.

Indeed, the position of this metal band 1 on the support cylinder 3 may vary.

The rails 41a and 41b are thus in contact with the applicator cylinder 20 and remove excess polymer crosslinkable by rubbing on said cylinder 20.

According to another variant represented in fig. 3, means 40 for removing excess crosslinkable polymer on the applicator cylinder 20 are formed, on the one hand, by two recovery cylinders, respectively 42a and 42b, of hard surface, such as metal, in contact with the applicator cylinder 20 in each zone located outside the zone in contact with said applicator cylinder 20 with the metal strip 1 and, on the other hand, by two rails, respectively 43a and 43b, metallic example, each in contact with a cylinder of recovery 42a and 42b.

The recovery cylinders 42a and 42b are dragged in rotation in the same direction as the cylinder applicator 20 and eventually they are cooled.

According to one more variant, the suppression means of excess crosslinkable polymer on the applicator cylinder 20 they are formed, on the one hand, by a recovery cylinder possibly cooled, hard surface, for example metallic, in contact with the applicator cylinder 20 and, on the other hand, by a for example metal, in contact with the cylinder Recovery. In this case, the recovery cylinder and the rail have a length equal to at least the length of the cylinder applicator 20.

Thus, excess crosslinkable polymer deposited on the applicator cylinder 20 on each side of the zone of application of this crosslinkable polymer on the metal strip 1 is transferred over recovery cylinders 42a and 42b and this excess crosslinkable polymer is separated from the cylinders of recovery 42a and 42b through the paths 43a and 43b.

Means for suppressing excess polymer crosslinked deposited on the applicator cylinder 20 avoid the have to add inserts to the level of slot 12 of the row of extrusion 11, to calibrate from its exit from row 11 the crosslinkable polymer layer 30 and accommodate variations of width and transverse placement of the metal band 1 within the limits of tolerances previously defined.

According to a variant, the two sides of the band metal 1 may be covered by a polymer film 31 crosslinkable

In this case, a device 10 of application of the film 31 on one side of the metal band 1 and it place another film 31 application device on the other side of said metal band 1.

The application of film 31 on each face of the metal band 1 can be separated or be simultaneous. For one simultaneous application, support cylinder 3 is suppressed and replaced by an applicator cylinder of the second device application. The applicator cylinder of each device forms a metal band support cylinder.

Moreover, the transverse position of the row of extrusion 11 can remain permanently centered with in relation to the metal band 1 having this extrusion row 11 on a mobile support transversely and connecting this row to the extrusion machine by a flexible 13, which allows adjust the position of this extrusion row 11 with respect to the metal band 1 depending on position variations transverse of said metal band 1 with respect to the cylinder of the support 3.

According to one more variant, you can deposit a lubricant on the applicator cylinder 20 outside the area in contact with the metal band 1, in order to facilitate the operation of the rails 41a and 41b to suppress the excess of crosslinkable polymer.

As an example, we will say that the formulation of the crosslinkable polymer mixture is performed as follows:

- 85% by weight of a polyol polyester called URALAC P1460 of the DSM Resins Company (Netherlands) that It has the following characteristics:

-

-OH average number by molecules; F_ {OH.moy} = 3

-

Hydroxyl index polyol | OH = 37 to 47

-

Mean molar mass (in mass) M_ {w} = 20000g / mol

-

Mean molar mass (in number of molecules) M_ {n} = 4090

-

Index of M_ {w} / M_ {n} polydispersity: | p = 4.9 (The Index of hydroxyl of the polyol | OH is defined as the amount Potash required -in mg- to neutralize all functions hydroxyl; we will then have: F_ {OH.moy} = | OH M_ {n} / 56100)

-

as hardener, 15% by mass of blocked isocyanate called VESTAGON BF 1540 of the HÜLS Company, consisting essentially of uretidione of IPDI

-

Average number of -NCO per molecule: F_ {iso.moy} = 2

-

Temperature of melting between 105 and 115 ° C

-

Temperature of crosslinking release = 160 ° C

-

Total amount of NCO radicals = 14.7 to 16% mass

-

Proportion of free NCO radicals (not blocked) <1% mass,

-

viscosity for a shear rate of 10s -1:

\ cdot a 120ºC: 900 Pa.s \ cdot a 130 ° C: 400 Pa.s \ cdot a 140ºC: 180 Pa.s \ cdot a 150ºC: 80 Pa.s

This mixture is entirely in state fluid and / or viscous from a temperature of 120ºC and its Rapid crosslinking temperature is between 170 and 250 ° C

The crosslinkable polymer can also be pigmented and charged for example at 40% and more by weight of oxide of titanium.

The coating device according to the invention allows, thanks to the use of an applicator cylinder deformable surface, get a polymer coating crosslinkable uniform thickness for example between 5 and 50 um and applied homogeneously on a metal strip that present an important roughness of amplitude comparable to the thickness of the film and this thanks to the perfect contact between the cylinder applicator and the surface of the strip to be coated, to despite the effects of flatness and thickness heterogeneity of The metal band.

The speed of the applicator cylinder can adjust to a level substantially higher or lower than the travel speed of the metal band to obtain a perfect coating continuity and excellent condition surface of this transferred crosslinkable polymeric coating to this metal band.

Moreover, the surface energy of the External shell of deformable material of the applicator cylinder is adapted to the crosslinkable polymer to allow a good coating spread on this applicator cylinder.

The coating device according to the invention can also be used for a metal band descending or horizontal.

The fact that the formation temperature of the layer is lower than the polymer crosslinking temperature is an important feature in the case of polymers thermosetting since the forced flow through a slot Extrusion involves significant stagnations of the polymer, which they are necessary for a good distribution of this polymer to the whole width of said extrusion slot and there is no risk at this level to a crosslinking of said polymer.

Moreover, the coating device according to the invention it allows to continuously coat metal bands of different widths or simultaneously cover several bands Metals arranged parallel to each other and avoid by means simple and effective fluctuations in width and placement transverse of the band or metal bands.

The coating device according to the invention makes it possible to facilitate regular and uniform feeding of the crosslinkable polymer coating, selecting the shape of better adapted food depending on the product in question use.

The interest of this wide choice is particularly important in the case of coatings highly reactive thermosetting materials whose feeding cannot be carried out at an elevated temperature close to the field of reactivity.

This device also allows, in the case of a chemical crosslinking process, raise the temperature of coating with crosslinkable polymer to reduce its viscosity and facilitate its transfer and its application on the band metallic

Indeed, the temperature of the matter supplied by the power system located in front of the applicator cylinder is limited to a lower value than the principle of crosslinking, to avoid any risk of evolution of the product in the feeding system.

Due to this temperature limitation, it is impossible to reduce the viscosity of the product to a level low enough to facilitate its transfer and its good arrangement on the metal band. Upon contact with the heated applicator cylinder, the matter that is about transfer can withstand very important heating, but for a very short time that avoids any risk of product crosslinking at this level.

Finally we will say that the device according to the invention allows to compensate for fluctuations in width or position transverse of the metal band in the course of the application and not worry about uniformity defects of the metal band, thus making a coating of uniform thickness on the surface on a non-uniform metal substrate.

Claims (29)

1. Continuous coating procedure of at least one metal band (1) for a fluid film (31) of crosslinkable polymer free of solvent or non-reactive diluent and whose softening temperature is greater than 50 ° C, having said film (31) a thickness less than that of the metal band, according to which: - the metal band is moved continuously (1) on at least one support cylinder (3), - is formed on an applicator cylinder (20) of deformable surface and forced flow at a higher temperature at the softening temperature of the crosslinkable polymer, a layer (30) of said melt crosslinkable polymer, which has a viscosity greater than 10 Pa.s under the conditions of formation of said layer, the forming temperature of this layer being (30) less than the temperature at the beginning of the crosslinking of the crosslinkable polymer and said applicator cylinder being entrained (20) rotating in the opposite direction to the direction of travel of the metal band (1), - is formed, on the applicator cylinder (20), the crosslinkable polymer film (31), - a total thickness transfer is made of the film (31), of the applicator cylinder on the metal strip (1), compressing this metal band between the support cylinder (3) and the applicator cylinder (20) to obtain a coating of homogeneous thickness. 2. The coating process according to claim 1, characterized in that the metal band (1) is previously heated to a temperature substantially equal to or greater than the temperature of the crosslinkable polymer film (31) and the softening temperature of this crosslinkable polymer. 3. Coating process according to claim 1 or 2, characterized in that the applicator cylinder (20) is heated to a temperature substantially equal to or greater than the forming temperature of the layer (30) and the softening temperature of this crosslinkable polymer . 4. Coating process according to claim 1, characterized in that the layer (30) is formed by extrusion and overlap. 5. Coating process according to claim 1, characterized in that the layer (30) is formed by extrusion and lamination. 6. The coating method according to claim 1, characterized in that the layer (30) is formed by spraying fluid crosslinkable polymer onto the applicator cylinder (20). 7. The coating process according to claim 1, characterized in that the layer (30) is formed on the applicator cylinder (20) from a previously made crosslinkable continuous polymer web. 8. The coating method according to any one of claims 1 to 7, characterized in that the internal temperature of the applicator cylinder (20) is adjusted to avoid damaging the deformable surface of this applicator cylinder (20). 9. The coating method according to any one of claims 1 to 8, characterized in that the tangential speed of the applicator cylinder (20) is adjusted in a proportion between 0.5 and 2 times the speed of movement of the metal strip (1). 10. Coating process according to any one of claims 1 to 9, characterized in that the fluid crosslinkable polymer layer (30) is formed with a width less than the width of the metal strip (1) to only coat a part of this metal band (1). 11. Coating process according to any of claims 1 to 10, characterized in that the layer (30) and the fluid crosslinkable polymer film (31) with a width greater than the width of the metal strip (1) are formed to cover the all of this metal band (1). 12. Coating method according to any of claims 1 to 9 or 11, characterized in that the crosslinkable polymer deposited in excess on the applicator cylinder (20) is removed. 13. Coating process according to any of claims 1 to 9, 11 or 12, characterized in that a lubricant is deposited on the applicator cylinder (20) outside the area that is in contact with the metal strip (1). 14. Continuous coating device at least one metal band (1) for a fluid film (31) of crosslinkable polymer free of solvent or non-reactive diluent and whose softening temperature is greater than 50 ° C, having said film (31) a thickness less than that of the metal band (1), comprising said device: - continuous means of dragging the band metallic (1), - at least one support cylinder (3) of the metal band (1), - training means (11, 12), on a applicator cylinder (20) with deformable surface and forced flow at a temperature above the softening temperature of the crosslinkable polymer, of a layer (30) of said crosslinkable polymer in molten state, with a viscosity greater than 10 Pa.s in the formation conditions of said layer, the temperature being formation of this layer (30) lower than the beginning temperature of crosslinking of the crosslinkable polymer and being dragged the said applicator cylinder (20) rotating in the opposite direction to direction of movement of the metal band (1) and forming the crosslinkable polymer film (31), - and the compression means of the metal band between the support cylinder (3) and the applicator cylinder (20) for effect a total thickness transfer of said film (31) of the applicator cylinder (20) on the metal strip (1) and obtain a homogeneous thickness coating. 15. Coating device according to claim 14, characterized in that it comprises means for preheating the metal strip (1) at a temperature equal to or greater than the temperature of the crosslinkable polymer film (31) and the softening temperature of this polymer crosslinkable 16. Coating device according to claim 14 or 15, characterized in that it comprises heating means of the applicator cylinder (20) at a temperature substantially equal to or greater than the forming temperature of the layer (30) and the softening temperature of This crosslinkable polymer. 17. Coating device according to claim 14, characterized in that the forced flow forming means of the layer (30) comprise an extrusion machine provided with a row (11) comprising an extrusion groove (12) and an organ of flow regulation arranged between the extrusion machine and the row (11). 18. Coating device according to claims 14 and 17, characterized in that the forced flow forming means of the layer (30) are formed by the row (11) in support against the surface of the applicator cylinder (20) and provided with means for adjusting the position of the edges of the extrusion groove (12) of said row (11) relative to the surface of the applicator cylinder (20). 19. Coating device according to claims 14 and 17, characterized in that the forced flow formation means of the layer (30) are formed by the row (11), layer stretching means (30) by adjusting the flow rate of passage of the row (11) and / or of the rotation speed of the applicator cylinder (20), means for regulating the position of the edges of the extrusion groove (12) of said row (11) in relation to the surface of the applicator cylinder (20) and by means of applying the layer (30) on said surface of the applicator cylinder (20). 20. Coating device according to claims 14 and 17, characterized in that the forced flow forming means of the layer (30) are formed by a projection system of fluid crosslinkable polymer on the applicator cylinder (20) to form said layer ( 30). 21. Coating device according to claims 14 and 17, characterized in that the forced flow forming means of the layer (30) are formed by an application system on the applicator cylinder (20) of a previously made crosslinkable polymer continuous band to form said layer (30). 22. Coating device according to any of claims 14 to 21, characterized in that it comprises means for regulating the internal temperature of the applicator cylinder (20) to avoid damaging the outer envelope (22) made of deformable material, of this applicator cylinder ( twenty). 23. Coating device according to any of claims 14 to 22, characterized in that it comprises means for regulating the tangential speed of the applicator cylinder (20) in a ratio between 0.5 and 2 times the speed of movement of the metal band (1). 24. Coating device according to any of claims 14 to 19, 22 or 23, characterized in that the means for applying the layer (30) on the applicator cylinder (20) comprise an air sheet directed on the applicator cylinder (20) at the level of the contact generator of said layer (30) on the indicated applicator cylinder (20). 25. Coating device according to any of claims 14 to 24, characterized in that the layer (30) and the fluid crosslinkable polymer film (31) have a width less than the width of the metal strip (1) for coating only a part of this metal band (1). 26. Coating device according to any of claims 14 to 24, characterized in that the layer (30) and the fluid crosslinkable polymer layer (31) have a width greater than the width of the metal strip (1) to cover all of the this metal band (1). 27. Coating device according to any of claims 14 to 24 or 26, characterized in that it comprises means (40) for removing excess crosslinkable polymer deposited on the applicator cylinder (20). 28. Coating device according to claim 27, characterized in that the elimination means (40) are formed by at least one rail (41a, 41b) in contact with the applicator cylinder (20) in each zone located outside the zone in contact of said applicator cylinder (20) with the metal strip (1). 29. Coating device according to claim 27, characterized in that the removal means (40) are formed, on the one hand, by at least one hard surface recovery cylinder (42a, 42b) in contact with the applicator cylinder (20) in each zone located outside the zone in contact of said applicator cylinder (20) with the metal band (1) and driven in rotation in the same direction as this applicator cylinder (20) and, on the other hand, for at least one raedera (43a, 43b) in contact with each recovery cylinder (42a, 42b).